Thanks for your modifications!
If you have time you can verify the lines "DetailPrint" and "MessageBox" in .nsi file.
For find the Maxthon folder, Mx_Updater check the registry key: HKEY_CURRENT_USER\Software\Maxthon3\Folder
If this key doesn't exist, the default folder is set to: $PROGRAMFILES\Maxthon3
The Maxthon portable version don't use registry, and if the portable Maxthon folder is not in "Program files" you need to select it manualy in Mx_Updater.
After this step Mx_Updater check the Maxthon.exe version in "$INSTDIR\Bin"
If the version is less than 4.8.8 = Maxthon Cloud (Webkit\npplugin)
If the version is greater than 4.8.8 = Maxthon NG (Blink\plugins)
Portable version have a Maxthon.exe in Bin folder? Or it's MaxthonPortable.exe (or other name)?

Fast search on Google for example.
Paste the good URL for Mx 4.4 translation.
Example for French translation: http://maxthon-fr.com/site/files/fr-fr.zip
This line dl the translaton file:
NSISdl::download http://maxthon-fr.com/site/files/fr-fr.zip "$TEMP\${PRODUCT_NAME}\fr-fr.zip"
This line extract the file:
nsUnzip::Extract "$TEMP\${PRODUCT_NAME}\fr-fr.zip" "/d=$TEMP\${PRODUCT_NAME}\Translation" /END
And this line copy the ini file on Maxthon Cloud folder:
CopyFiles "$TEMP\${PRODUCT_NAME}\Translation\*.*" "$INSTDIR"
For French version, the .zip containt "Language" folder.
If not for Russian version, add "\Language" in copy line:
CopyFiles "$TEMP\${PRODUCT_NAME}\Translation\*.*" "$INSTDIR\Language"

Sources updated for the support of the new Flash Player DLL names.
In first post I've forgotten one step before the compilation :
Download nsUnzip plugin and extract nsUnzip.dll to the "%ProgramFiles%\NSIS\Plugins" folder.